Catalysts for the production of ethylene oxide from ethylene and molecular oxygen are generally supported silver catalysts. Such catalysts are typically promoted with alkali metals. The use of small amounts of the alkali metals potassium, rubidium and cesium were noted as useful promoters in supported silver catalysts in U.S. Pat. No. 3,962,136, issued Jun. 8, 1976, and U.S. Pat. No. 4,010,115, issued Mar. 1, 1977. The use of other co-promoters, such as rhenium, or rhenium along with sulfur, molybdenum, tungsten and chromium is disclosed in U.S. Pat. No. 4,766,105, issued Aug. 23, 1988, and U.S. Pat. No. 4,808,738, issued Feb. 28, 1989. U.S. Pat. No. 4,908,343, issued Mar. 13, 1990, discloses a supported silver catalyst containing a mixture of a cesium salt and one or more alkali metal and alkaline earth metal salts.
The use of alumina-based catalyst carriers has been previously described in a number of patents such as, for example, U.S. Pat. No. 5,100,859, issued Mar. 31, 1992, U.S. Pat. No. 5,055,442, issued Oct. 8, 1991, U.S. Pat. No. 5,037,794, issued Aug. 6, 1991, and U.S. Pat. No. 4,874,739, issued Oct. 17, 1989. These alumina carriers have a wide variety of potential applications in the catalytic field and are especially useful where the alumina base is alpha alumina and the application is one in which abrasion resistance is a desirable feature.